Off-Spec Crude Oil Upgrading

ABSTRACT

Included are processes and systems for upgrading off-spec crude oil. The processes and systems use a separator to take a sharp cut of a blend of off-spec crude oil and natural gas liquids (NGL) or butanes, so as to recover a valuable crude oil product from the separator. The processes and systems can be performed and located on an oil production site.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/484,087 filed Apr. 11, 2017 by Eric Prim entitled, “Off-Spec Crude Oil Upgrading”, which is incorporated by reference herein as if reproduced in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

An oil production site generates crude oil from a subterranean formation. In some cases, the crude oil obtained from the subterranean formation has little value due to undesirable characteristics. For example, West Texas and North Dakota have some subterranean formations that can produce crude oil having a large amount of C₃− hydrocarbons. The large amount of C₃− hydrocarbons gives the crude oil properties (e.g., vapor pressure) that exceed pipeline specifications, which makes production of those subterranean formations undesirable.

If crude oil with properties that do not meet the pipeline specifications is produced at the oil production site, a separation step can be performed on-site to prepare this type of crude oil for pipeline transport. For example, the crude oil from the subterranean formation can be heated in a fire tube heat exchanger and then flashed in a single stage so as to remove C₁-C₃ hydrocarbons from the oil. However, such a technique causes valuable C₄-C₈ hydrocarbons to be removed from the oil. Thus, there is a need for on-site techniques that can make crude oil recovery from these types of formations desirable.

SUMMARY

An off-spec crude oil upgrading process comprising combining a first stream comprising an off-spec crude oil with a second stream comprising natural gas liquids (NGL) or butane to yield a blend of the off-spec crude oil and the NGL or butane, and separating the blend into an overhead stream comprising C₃− hydrocarbons and light compounds and a bottom stream comprising a crude oil product comprising the NGL or butane.

An off-spec crude oil upgrading process comprising combining an off-spec crude oil with NGL or butane to yield a blend comprising the off-spec crude oil and the NGL or butane, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) of greater than about 10 pounds per square inch (psi), and controlling an amount of C₄ hydrocarbons recovered from an overhead stream of a separator such that a crude oil product produced by the separator has a RVP of about 8 pounds per square inch absolute (psia) to about 25 psia.

A system for off-spec crude oil upgrading comprising a blend comprising an off-spec crude oil and NGL or butane, and a separator configured to separate the blend into an overhead stream comprising C₃− hydrocarbons and light compounds and a bottom stream comprising a crude oil product comprising the NGL or butane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one embodiment of a process flow diagram for the upgrading of off-spec crude oil.

FIG. 2 illustrates another embodiment of a process flow diagram for the upgrading of off-spec crude oil.

FIG. 3 illustrates another embodiment of a process flow diagram for the upgrading of off-spec crude oil that includes pre-treatment of the oil from the well.

FIG. 4 illustrates another embodiment of a process flow diagram for the upgrading of off-spec crude oil that includes pre-treatment of the oil from the well.

FIG. 5 illustrates a graph of temperature versus tray position for the distillation column in Example 2.

FIG. 6 illustrates a graph of pressure versus tray position for the distillation column in Example 2.

FIG. 7 illustrates a graph of vapor and liquid molar flow versus tray position for the distillation column in Example 2.

FIG. 8 illustrates a graph of density and molecular weight versus tray position for the distillation column in Example 2.

FIG. 9 illustrates a graph of the mole fraction of methane, nitrogen, and oxygen versus tray position for the distillation column in Example 2.

FIG. 10 illustrates a graph of the K-value for nitrogen and methane versus tray position for the distillation column in Example 2.

FIG. 11 illustrates another embodiment of a process flow diagram for the upgrading of off-spec crude oil.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed processes and/or systems may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents.

It has been unexpectedly found that some crude oils contain problematic amounts of methane, ethane, and propane which cause the oil to be off pipeline specifications (herein “off-spec”). It has also been unexpectedly found that removing, on the oil-production site, only methane, ethane, and propane but not removing substantial amounts of C₄ and C₅ hydrocarbons according to the techniques described herein can result in an oil product that meets pipeline specifications and has greater volume than prior off-spec treatment methods. Additionally or alternatively, it has been found that controlling the amount of C₄ hydrocarbons recovered from an overhead stream of a separator that receives the off-spec crude oil, such that substantially all the C₃− hydrocarbons (e.g., methane, ethane, and propane) are recovered from the overhead stream of the separator, optionally with a controlled amount of C₄ hydrocarbons, can result in an oil product which meets pipeline specifications and has greater volume than prior off-spec treatment methods.

The processes 100, 200, 300, and 400 shown in FIGS. 1-4 can be performed on oil-production site 101 where the off-spec crude oil is produced. The oil-production site 101 is upstream of a pipeline. The processes and systems disclosed herein can be coupled to the pipeline via a stream of the disclosed separator; alternatively, the processes and systems disclosed herein can be coupled to the pipeline via storage tanks and/or any other process equipment used to prepare the crude oil product and that is/are coupled to the disclosed separator.

FIG. 1 illustrates an off-spec crude oil upgrading process 100. The process 100 is directed to removing the C³⁻ hydrocarbons and optionally some of the C₄ hydrocarbons from the off-spec crude oil found in stream 1 and taking advantage of the available RVP space by adding a stream (e.g., stream 2) comprising C₄ or C₄₊ hydrocarbons before removal of the C³⁻ hydrocarbons. RVP space may be defined as a difference between a pipeline's RVP limit (e.g., a pipeline specification) and a particular stream's RVP. In FIG. 1, stream 2 comprising C₄ or C₄₊ hydrocarbons is blended with the off-spec crude oil in stream 1 in a mixer 110 prior to removal of the C³⁻ hydrocarbons in the separator 150. Alternative configurations contemplate that stream 2 can feed directly to the separator 150, as shown in FIG. 2, or stream 2 can be added to a crude oil product in stream 14 obtained from the separator 150, as shown in FIG. 11.

The process 100 can begin with receiving a first stream 1 containing the off-spec crude oil, for example, from an oil-production site 101 that generates the crude oil from a subterranean formation. First stream 1 may have a temperature ranging from about 80 degrees Fahrenheit (° F.) to about 100° F. (e.g., 90° F.); a pressure ranging from about 40 psia to about 60 psia (e.g., 50 psia); a standard ideal liquid volume flow of about 20,000 barrels/day to about 30,000 barrels/day (e.g., 25,000 barrels/day); a specific gravity (60/60) ranging from about 0.7000 to about 0.8000 (e.g., 0.7395); and an American Petroleum Institute (API) gravity ranging from about 59 to about 60 (e.g., 59.85). The off-spec crude oil in stream 1 can contain a spectrum of hydrocarbons, for example, C₁ to C₃₀ hydrocarbons. That is, the off-spec crude oil can include C³⁻ hydrocarbons (e.g., methane, ethane, propane, or combinations thereof) in addition to heavier hydrocarbons (e.g., C₄+ hydrocarbons). The off-spec crude oil in stream 1 can have a Reid Vapor Pressure (RVP) of greater than 10 psi due to the presence of the C³⁻ hydrocarbons. While this RVP value is technically a suitable value for sale in some cases, the presence of the C³⁻ hydrocarbons is problematic and undesirable for most pipeline specifications.

RVP values referred to herein can be measured by any means known in the art with the aid of this disclosure, for example, by standardized methods: American Society for Testing and Materials (ASTM) D323 or International Organization for Standardization (ISO) 3007. It is contemplated that the off-spec crude oil can be sweet (e.g., less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 parts per billion (ppb) S and/or less than 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 parts per billion (ppb) CO₂) or sour (contains one or more sulfur-containing compounds and/or CO₂ above levels considered sweet). The sulfur-containing compounds, CO₂, or combinations thereof are within the scope of “light compounds” as used herein. “Light compounds” can also include gases such as hydrogen, nitrogen, oxygen, or combinations thereof.

The process 100 can further include receiving a second stream 2 comprising C₄ or C₄₊ hydrocarbons. The second stream 2 may include a temperature ranging from about 70° F. to about 90° F. (e.g., 80° F.); a pressure ranging from about 230 psia to about 250 psia (e.g., 240 psia); and a standard ideal liquid volume flow of about 3,500 barrels/day to about 4,500 barrels/day (e.g., 4,000 barrels/day). In an aspect, the second stream 2 comprises natural gas liquids (NGL). The NGL can comprise C₂ to C₇ hydrocarbons, for example. Alternatively, the second stream 2 can be butane. In embodiments where the second stream 2 is butane, the butane can be pure butane. “Pure butane” is defined as greater than 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.9, 99.99, or 99.999 weight percent (wt %) butane based on a total weight of the second stream 2. The embodiments are distinguished in that when the second stream 2 contains NGL, the NGL can contain butanes such as n-butane and i-butane among the other components of the NGL; whereas, when the second stream 2 is butane, it is intended that the second stream 2 contains butane (e.g., as n-butane, isobutane, or both) in the amounts disclosed herein (e.g., in concentrations known in the art to be considered butane, or concentrations appropriate for “pure butane”) to the exclusion of any significant amounts of other hydrocarbons (e.g., C₂, C₃, C₅, C₆, C₇ hydrocarbons) that are otherwise contained in NGL.

The process 100 can further include combining the first stream 1 with the second stream 2 in a mixer or blender 110 to yield a blended stream 3 comprising the i) the off-spec crude oil and ii) the NGL or butane. In embodiments where the second stream 2 contains NGL, the blended stream 3 can contain the C₁ to C₃₀ hydrocarbons of the off-spec crude oil mixed with the C₂ to C₇ hydrocarbons of the NGL, as well as any sulfur-containing compounds and/or CO₂ present in the off-spec crude oil and/or the NGL. In embodiments where the second stream 2 is butane, the blended stream 3 can contain the C₁ to C₃₀ hydrocarbons of the off-spec crude oil mixed with butane, as well as any sulfur-containing compounds and/or CO₂ present in the off-spec crude oil.

NGL can be obtained from a natural gas production site or from a NGL production facility, for example, as a NGL rich stream as described in any of U.S. Pat. No. 8,505,332, 9,200,833, or 9,574,823, each of which is incorporated by reference in its entirety. Butane can be obtained from any process stream, for example, from a separator configured to separate butane from NGLs. The NGLs are generally available at the oil-production site 101.

In embodiments of the process 100 in which the off-spec crude oil is sweet and the second stream 2 comprises NGL, the NGL combined with the off-spec crude oil can be sweet NGL or sour NGL, where the sour NGL can contain only H₂S and CO₂ as the sour compounds. In embodiments of the process 100 in which the off-spec crude oil is sour and the second stream 2 comprises NGL, the NGL combined with the off-spec crude oil can be sweet NGL or sour NGL, where the sour NGL can contain H₂S, CO₂, other sulfur-containing compounds, or combinations thereof.

In embodiments of the process 100, the blended stream 3 can experience one or more processing steps before the blended stream 3 is fed to a separator 150. For example, as shown in FIG. 1, the first stream 1 and the second stream 2 can be combined using mixer 110 to form the blended stream 3. The blended stream 3 then can be heated in a first heat exchanger 130 to form heated blended stream 4. The heated blended stream 4 can have a temperature higher than a temperature of the blended stream 3. The heated blended stream 4 can then flow through valve 140 to form a let-down stream 5 that feeds to the separator 150. Further blending can occur in the separator 150. Let-down stream 5 can have a pressure lower than a pressure of the heated blended stream 4. As can be seen in FIG. 1, the let-down stream 5 can feed to the separator 150 at a location near the top of the separator 150. In FIG. 1, the let-down stream 5 feeds to the separator 150 between the second stage/tray and the third stage/tray of the separator 150.

Alternatively, the blended stream 3 can feed directly to the separator 150. That is, it is contemplated the blended stream 3, first stream 1, second stream 2, or combinations thereof experience no processing prior to feeding to the separator 150. Further blending can occur in the separator 150.

FIG. 1 also shows a pump 120 can be included before stream 1 and can be configured to facilitate flow of the off-spec crude oil in stream 1A to a pressure in stream 1. In FIG. 1, the pump 120 can also be configured to provide motive force for i) pumping the off-spec crude oil to the mixer 110, ii) pumping the blended stream 3 comprising the first stream 1 and the second stream 2 to the separator 150, or both i) and ii). In other embodiments, the pump 120 may not be needed, and thus may not be used in the process 100.

The process 100 can further include separating the blend of the first stream 1 and the second stream 2 in the separator 150 into i) an overhead stream 7 comprising C₃− hydrocarbons and light compounds and ii) a bottom stream 11 comprising the crude oil product. The separation can take place in separator 150.

FIG. 1 shows the separator 150 can be configured as a distillation column. The separator 150 and any associated equipment (e.g., condenser unit 160 and/or reboiler 170 described herein) can be configured to take a sharp cut between C₃ hydrocarbons and C₄ hydrocarbons, such that compounds of C₃ hydrocarbons and lighter (e.g., C₃− hydrocarbons and other non-hydrocarbon light gases) flow overhead in the overhead stream 7 and are recovered as reject vapors in the stream 10 in FIG. 1, while compounds of C₄ hydrocarbons and heavier (C₄+ compounds) flow from the bottom of the separator 150 in the bottom stream 11 and recovered as the crude oil product in the stream 14. The crude oil product may include a temperature of about 360.0° F. to about 370.0° F. (e.g., 364.6° F.); a pressure of about 150 psia to about 250 psia (e.g., 200 psia); a standard ideal liquid volume flow ranging from about 20,000 barrels/day to about 30,000 barrels/day (e.g., 27,580 barrels/day); Reid vapor pressure at 37.8 degrees Celsius (° C.) is 13.41 psia; API gravity ranging from about 60 to about 65 (e.g., 62.81); and a specific gravity (60/60) ranging from about 0.7000 to about 0.7300 (e.g., 0.7282).

The term “sharp cut” can mean i) less than about 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 wt % butane (n-butane and/or i-butane) is contained in the reject vapors based on a total weight of the reject vapors, ii) less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.1, or 0.01 wt % propane is contained in the crude oil product based on a total weight of the crude oil product, iii) less than about 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 wt % butane (n-butane and/or i-butane) is contained in the reject vapors based on a total weight of the blend which feeds to the separator 150, iv) less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt % propane is contained in the crude oil product based on a total weight of the blend which feeds to the separator 150, or v) combinations thereof.

The temperature of the separator 150 can vary from top to bottom, with the top having a lower temperature than the bottom. Moreover, it is contemplated that each stage of the separator 150 can have progressively higher temperature than the last from top to bottom of the separator 150. The range of temperatures in the separator 150 can be about 50° F. (10° C.) to about 400° F. (204° C.); alternatively, about 100° F. (38° C.) to about 350° F. (177° C.); alternatively, about 150° F. (66° C.) to about 300° F. (149° C.).

The separator 150 can be adiabatic, or the pressure can vary from top to bottom. One or more pressures of the separator 150 can be about 40 psia (0.276 megapascal absolute (MPaa)) to about 250 psia (1.72 MPaa); alternatively, about 175 psia (1.21 MPaa) to about 225 psia (1.55 MPaa); alternatively about 190 psia (1.31 MPaa) to about 210 psia (1.45 MPaa); alternatively, about 195 psia (1.34 MPaa) to about 205 psia (1.41 MPaa); alternatively, about 195 psia (1.34 MPaa) to about 200 psia (1.38 MPaa). Mpaa is megapascals absolute, similar to how psia is pounds per square inch absolute.

The separator 150 can include a condenser unit 160. The condenser unit 160 can include a condenser and a reflux drum. The overhead stream 7 of the separator 150 can flow to the condenser of condenser unit 160 (e.g., a heat exchanger), which is configured to condense at least a portion of the overhead stream 7 into a two-phase mixture comprising a liquid phase and a vapor phase. The partially condensed overhead stream 7 can then flow from the condenser to the reflux drum configured to separate the overhead stream 7 into the vapor phase (e.g., containing reject vapors as described herein) in stream 10 and the liquid phase in reflux stream 9. The reject vapors include the undesired methane, ethane, and propane in the off-spec crude oil. Stream 10 may have a temperature ranging from about 90° F. to about 110° F. (e.g., 99.01° F.); a pressure of about 190 psia to about 200 psia (e.g., 195.0 psia); and a standard ideal liquid volume flow ranging from about 1400 barrels/day to about 1500 barrels/day (e.g., 1424 barrels/day). It is contemplated that the reject vapors can include small amounts of butane (e.g., n-butane and/or i-butane). For example, the reject vapors can include less than 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 wt % butane based on a total weight of the reject vapors. The reflux stream 9 can be a liquid stream which recycles back to the separator 150 as reflux, at the top of the column. In FIG. 1, the reflux stream 9 feeds between the first and second stage/tray at the top of the column. Heat flow from condenser unit 160 may range from about 5,000,000 British thermal units per hour (Btu/hr) to about 6,000,000 Btu/hr (e.g., 5,683,000 Btu/hr).

The separator 150 can include a reboiler 170. The reboiler 170 can be a vessel configured to heat the bottom stream 11 of the separator 150 such that a portion of the bottom stream 11 rises back into the separator 150 as vapor 12 between the last two stages/trays, and another portion of the bottom stream 11 flows from the reboiler 170 as a blended crude product in the stream 14. The components of the blended crude product can be collectively referred to as the crude oil product. It is contemplated that the crude oil product can include 0 wt % light compounds, 0 wt % methane, 0 wt % ethane, or combinations thereof, based on a total weight of the crude oil product. It is additionally or alternatively contemplated that the crude oil product can include less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.1, or 0.01 wt % propane based on a total weight of the crude oil product. In an embodiment, the crude oil product can have a RVP in a range of about 8 psia to about 14 psia. Heat flow from reboiler 170 may range from about 30,000,000 Btu/hr to about 40,000,000 Btu/hr (e.g., 36,920,000).

The crude oil product can flow via stream 14 to the pipeline for sale; alternatively, to storage or to further processing. An example of further processing is shown in FIG. 1, where the crude oil product can flow to the first heat exchanger 130 that is configured to cool the crude oil product to form cooled crude oil produced in stream 15. In an embodiment and as shown in FIG. 1, the crude oil product of stream 14 is cooled in a cross-exchange relationship with the blend of the first stream 1 and the second stream 2. That is, the first heat exchanger 130 is a cross-exchanger where the crude oil product in stream 14 is used to heat the blended stream 3. Put another way, the first heat exchanger 130 is a cross-exchanger where the blend of the first stream 1 and the second stream 2 in blended stream 3 is used to cool the crude oil product in stream 14. The cooled crude oil product can flow from the first heat exchanger 130 in stream 15 to a second heat exchanger 180. The second heat exchanger 180 can be configured to remove heat from the cooled crude oil product to form a further cooled crude oil product in stream 16. The second heat exchanger 180 can be configured to use a heat transfer fluid to remove heat from the cooled crude oil product to form the further cooled crude oil product.

FIG. 1 also shows a control and/or monitoring system 190 can be utilized in the process 100. For example, in FIG. 1, control and/or monitoring system 190 can be coupled with stream 10 to measure and/or control an amount (e.g., via concentration and/or flow) of one or more components (e.g., hydrogen, nitrogen, methane, ethane, propane, n-butane, i-butane, or combinations thereof) in stream 10. Additionally or alternatively, control and/or monitoring system 190 can be coupled with stream 14 to measure and/or control an amount (e.g., via concentration and/or flow) of one or more components in stream 14. Use of equipment known in the art with the aid of this disclosure which is configured to control and/or monitor process components is contemplated in the control and/or monitoring system 190. Embodiments also can include an RVP analyzer in stream 11 and/or stream 14 to control the temperature of the separator 6 to produce RVP values for the crude oil product within the desired range.

FIG. 2 illustrates another off-spec crude oil upgrading process 200. Like the process 100 of FIG. 1, the process 200 of FIG. 2 is performed at an oil-production site 101 upstream of a pipeline. The process 200 is directed to removing the C³⁻ hydrocarbons and optionally some of the C₄ hydrocarbons from the off-spec crude oil found in stream 1 and taking advantage of the available RVP space by adding a stream (e.g., stream 2) comprising C₄ or C₄₊ hydrocarbons simultaneously with removal of the C³⁻ hydrocarbons. The process 200 of FIG. 2 is similar to that shown in FIG. 1, except as shown in FIG. 2, the off-spec crude oil in stream 1 and the NGL or butane in stream 2 can each feed directly to the separator 150 without blending the first stream 1 with the second stream 2 outside the separator 150. In such an embodiment, the blending occurs only inside the separator 150 at the oil-production site 101. Like the process 100 of FIG. 1, the process 200 of FIG. 2 is performed at an oil-production site 101 upstream of a pipeline.

The process 200 can begin with feeding the first stream 1 comprising the off-spec crude oil to the separator 150 and feeding the second stream 2 comprising natural gas liquids (NGL) or butane to the separator 150. Stream 1 can feed to the separator 150 at the fourth stage/tray of the separator 150. Stream 2 can feed to the separator 150 between the second stage/tray and the third stage/tray of the separator 150. Stream 1 and stream 2 can have the same composition and properties as described for these streams in FIG. 1.

FIG. 2 shows the first stream 1 and the second stream 2 experience no processing, including mixing/blending and heating, prior to feeding into the separator 150. However, it is contemplated that the first stream 1 and/or the second stream 2 can be heated prior to feeding to the separator 150, for example, using the first heat exchanger 130 in cross-exchange configuration as shown in FIG. 1. It is also contemplated that the pump 120 of FIG. 1 can be used in stream 1 of process 200 to facilitate flow of the off-spec crude oil to the separator 150.

The process 200 of FIG. 2 can further include recovering i) the overhead stream 7 comprising C₃− hydrocarbons and light compounds and ii) the bottom stream 11 comprising a crude oil product comprising the NGL or butane from the separator 150. The technique of recovering can include separating the blend of the first stream 1 and the second stream 2 in the separator 150 into i) an overhead stream 7 comprising C₃− hydrocarbons and light compounds and ii) a bottom stream 11 comprising a crude oil product. The separation can take place in the separator 150. A condenser unit 160 and reboiler 170 can be utilized as described for FIG. 1 to obtain reject vapors in stream 10 and the crude oil product in stream 14.

Optional embodiments of process 200 contemplate that the crude oil product in stream 14 can be once or twice cooled, such as that shown in FIG. 1 using first heat exchanger 130 and/or second heat exchanger 180, so as to form a cooled crude oil product (e.g., similar to stream 15) and/or a further cooled crude oil product (e.g., similar to stream 16).

Optional embodiments of process 200 also include use of a control and/or monitoring system 190 coupled with stream 10 to measure and/or control an amount (e.g., via concentration and/or flow) of one or more components (e.g., hydrogen, nitrogen, methane, ethane, propane, n-butane, i-butane, or combinations thereof) in stream 10. Additionally or alternatively, control and/or monitoring system 190 can be coupled with stream 14 to measure and/or control an amount (e.g., via concentration and/or flow) of one or more components in stream 14. Use of equipment known in the art with the aid of this disclosure which is configured to control and/or monitor process components is contemplated in the control and/or monitoring system 190. Embodiments also can include an RVP analyzer in stream 11 and/or stream 14 to control the temperature of the separator 150 to produce RVP values for the crude oil product within the desired range.

FIG. 3 illustrates an off-spec crude oil upgrading process 300 that includes pre-treatment of the raw crude produced from the subterranean formation. Like the process 100 of FIG. 1, the process 300 of FIG. 3 is performed at an oil-production site 101 upstream of a pipeline. The process 300 is directed to removing the C³⁻ hydrocarbons and optionally some of the C₄ hydrocarbons from the off-spec crude oil found in stream 1 and taking advantage of the available RVP space by adding a stream (e.g., stream 2) comprising C₄ or C₄₊ hydrocarbons before removal of the C³⁻ hydrocarbons. In FIG. 3, stream 2 comprising C₄ or C₄₊ hydrocarbons is blended with the off-spec crude oil in stream 1 in a mixer 110 prior to removal of the C³⁻ hydrocarbons in the separator 150.

In the process 300, a pre-treatment unit 310 can pre-treat raw crude in stream 301 obtained from the subterranean formation at the oil-production site 101. For example, the pre-treatment unit 310 can be configured to remove methane and water from the raw crude in stream 301. Such technique can produce stream 302 comprising methane and stream 303 comprising water. The methane in stream 302 can be flared, sold as a natural gas stream, or as shown in FIG. 3, the stream 302 can feed to the mixer 110 for mixing with stream 1 and stream 2. As a result, the composition of the blended stream 3, the heated stream 4, and the let-down stream 5 can include methane (although it is contemplated that these streams can also contain small amounts of methane in NGL).

After pre-treatment of the raw crude as described above, the process 300 is the same as the process 100 described for FIG. 1. The methane delivered to the mixer 110 in stream 302 can flow in the process 300 in streams 3, 4, 5, 7, and 10. The methane can leave the process 300 as part of the reject vapors in stream 10. The streams in the process 300 are otherwise the same as described in process 100.

FIG. 4 illustrates an off-spec crude oil upgrading process 400 that includes pre-treatment of the stream 301 obtained from the subterranean formation. Like the process 100 of FIG. 1, the process 400 of FIG. 3 is performed at an oil-production site 101 upstream of a pipeline. The process 400 is directed to removing the C³⁻ hydrocarbons and optionally some of the C₄ hydrocarbons from the off-spec crude oil found in stream 1 and taking advantage of the available RVP space by adding a stream (e.g., stream 2) comprising C₄ or C₄₊ hydrocarbons simultaneously with removal of the C³⁻ hydrocarbons.

The process 400 of FIG. 4 is similar to that shown in FIG. 2, except that a pre-treatment unit 310 is included in the process 400 and configured to pre-treat raw crude in stream 301 obtained from the subterranean formation at the oil-production site 101. For example, the pre-treatment unit 310 can be configured to remove methane and water from the raw crude in stream 301. Such technique can produce stream 401 comprising methane and stream 303 comprising water. The methane in stream 401 can be flared, sold as a natural gas stream, or as shown in FIG. 4, the stream 401 can feed directly to the separator 150. In FIG. 4, the stream 401 is shown as feeding to the separator 150 at the first stage/tray at a location above stream 1 and stream 2. It is contemplated that stream 401 can alternatively combine with stream 1 or stream 2, and the methane contained in stream 401 can flow in stream 1 or stream 2 into the separator 150.

After pre-treatment of the raw crude as described above, the process 400 is the same as the process 200 described for FIG. 2. The methane delivered to the separator in stream 401 can flow in the process 400 in streams 7 and 10. The methane can leave the process 400 as part of the reject vapors in stream 10. The streams in the process 400 can otherwise be the same as described in process 200.

An additional or alternative process for off-spec crude oil upgrading contemplated by the disclosure is controlling an amount of C₄ hydrocarbons recovered from the overhead stream 7 of the separator 150 such that a crude oil product (having the C₃− hydrocarbons of the off-spec crude substituted with butane or NGL components) having a RVP of about 8 psia to about 25 psia, alternatively of about 8 to about 14 psia, is recovered from an off-spec crude oil having a RVP of greater than about 10 psi. The amount of C₄ hydrocarbons recovered from the overhead stream 7 of the separator 150 can be measured in stream 10 by the control and/or monitoring system 190 as shown in FIGS. 1-4. Stream 10 comprises the vapor phase of reject vapors recovered from the condenser unit 160. The process which controls the amount of C₄ hydrocarbons recovered from the overhead stream 7 can also include monitoring the amount of C₄ hydrocarbons recovered from the bottom stream 11 of the separator 150. The amount of C₄ hydrocarbons recovered from the bottom stream 11 of the separator 150 can be measured by the control and/or monitoring system 190 in stream 14 as shown in FIGS. 1-4. Stream 14 comprises the crude oil product recovered from the bottom stream 11 of the separator 150.

The amount of C₄ hydrocarbons recovered from the overhead stream 7 can be any of the concentrations disclosed herein for a “sharp cut.” Additionally or alternatively, the amount of C³⁻ hydrocarbons recovered from the bottom stream 11 can any of the concentrations disclosed herein for a “sharp cut.” Additionally or alternatively, the amount of compounds lighter than propane recovered from the overhead stream 7 can be any amount or concentration disclosed herein.

The process of controlling an amount of C₄ hydrocarbons recovered from the overhead stream 7 of the separator 150 can be used in combination with any other process step disclosed herein. The step of controlling an amount of C₄ hydrocarbons recovered from the overhead stream 7 of the separator 150 can include adjusting, by the control and/or monitoring system 190, an operating condition of the separator 150 so as to recover a target amount of C₄ hydrocarbons in the vapor phase of reject vapors in stream 10. The operating condition can include one or more of pressure, temperature, number of trays/stages, type of trays/stages, feed rate of off-spec crude oil in stream 1, feed rate of NGL or butane in stream 2, condenser unit 160 temperature, reboiler 170 temperature, reflux ratio of the separator 150, reboil ratio of the separator 150, tray spacing in the separator 150, diameter of the separator 150, tray/stage entrance of the feeds (e.g., adjust stream 5 feed from between stages 3 and 4 instead to stages 2 and 3), or combinations thereof.

FIGS. 1-4 also illustrate systems contemplated by this disclosure. Generally, each of FIGS. 1-4 shows a system comprising 1) a blend (e.g. in stream 3, 4, or 5) comprising i) an off-spec crude oil (e.g., from stream 1) blended with ii) NGLs or butane (e.g., from stream 2), and 2) a separator (e.g., separator 150) configured to separate the blend into i) an overhead stream 7 comprising C₃− hydrocarbons and light compounds and ii) a bottom stream 11 comprising a crude oil product. In the system, the off-spec crude oil can have a RVP greater than about 10 psi. Additionally or alternatively, the crude oil product in the system has a RVP of about 8 psia to about 25 psia, alternatively, of about 8 psia to about 14 psia. The separator 150 can be configured to take a sharp cut such that C₃− hydrocarbons and light compounds flow in the overhead stream 7, and compounds of C₄ hydrocarbons and heavier are recovered in the bottom stream 11. The separator 150 can be configured such that less than about 0.1 wt % butane is contained in reject vapors recovered from the overhead stream 7 based on a total weight of the reject vapors, less than about 10 wt % propane is contained in the crude oil product based on a total weight of the crude oil product, less than about 0.1 wt % butane is contained in the reject vapors based on a total weight of the blend which feeds to the separator 150, less than about 10 wt % propane is contained in the crude oil product based on a total weight of the blend which feeds to the separator 150, or a combination thereof.

The system(s) disclosed herein can further include any combination of other equipment and stream(s) disclosed herein, for example, any of stream 1A, stream 1, stream 2, stream 3, stream 4, stream 5, stream 7, stream 9, stream 10, stream 11, stream 12, stream 14, stream 15, stream 16, mixer 110, pump 120, first heat exchanger 130, valve or let down valve 140, separator 150, condenser unit 160, reboiler 170, second heat exchanger 180, control and/or monitoring system 190, any control wiring, any equipment for measuring a process condition (e.g., transducer, thermocouple), or combinations thereof. For example, the system can further include a mixer 110 configured to receive the off-spec crude oil from stream 1 and the NGL or butane from stream 2 upstream of the separator 150, and further configured to form the blend. The system can also include a first heat exchanger 130 configured as a cross heat exchanger, wherein the first heat exchanger 130 is configured to cool the crude oil product in stream 14 to form a cooled crude oil product in stream 15 and to heat the blend in a blended stream 3 to form a heated blended stream 4. The system can also include a let-down valve 140 configured to receive the heated blended stream 4 and to let-down a pressure of the heated blended stream 4 to form a let-down stream 5, wherein the let-down stream 5 is configured to feed the blend to the separator 150. The system can further include a second heat exchanger 180 configured to cool the cooled crude oil product in stream 15 to form a further cooled crude oil product in stream 16, wherein the second heat exchanger 180 is optionally coupled to a storage tank or to a pipeline. The system can further include a pre-treatment unit 310 configured to separate an impurity from a raw crude in stream 301, wherein the pre-treatment unit 310 is further configured to produce a methane stream 302/401, the off-spec crude oil in stream 1, and an impurity stream in stream 303. The mixer 110 can be configured to receive stream 301, or stream 401 can be configured to feed directly to a top of the separator 150. The system can also include a control and/or monitoring system 190 coupled to at least one of the overhead stream 7 and the bottom stream 11, wherein the control and/or monitoring system 190 is configured to control an amount of C₄ hydrocarbons recovered from the overhead stream 7 of the separator 150 such that the crude oil product produced by the separator has a RVP of about 8 psia to about 25 psia, alternatively of about 8 psia to about 14 psia, due to the presence of NGLs or butane blended with the off-spec crude oil.

The blend of the system(s) can be formed outside of and upstream of the separator 150, while in other embodiments, the blend can be formed inside the separator 150. In embodiments where the blend is formed inside the separator 150, the off-spec crude oil can be fed in stream 1 to the separator 150 separately from the NGL or butane which is fed in stream 2 to the separator 150.

The separator is described herein as a distillation column. However, it is contemplated the separator described herein may be any of a variety of process equipment, including the distillation column, suitable for separating a stream into two separate streams having different compositions, states, temperatures, and/or pressures and having the ability to perform “sharp cut” disclosed herein. For example, one or more of the separators may be a column having trays, packing, or some other type of complex internal structure. Examples of such columns include scrubbers, strippers, absorbers, adsorbers, packed columns, and distillation columns having valve, sieve, or other types of trays. Such columns may employ weirs, downspouts, internal baffles, temperature, and/or pressure control elements. Such columns may also employ some combination of reflux condensers and/or reboilers, including intermediate stage condensers and reboilers. Alternatively, one or more of the separators may be a phase separator. A phase separator is a vessel that separates an inlet stream into a substantially vapor stream and a substantially liquid stream, such as a knock-out drum or a flash drum. Such vessels may have some internal baffles, temperature, and/or pressure control elements, but generally lack any trays or other type of complex internal structure commonly found in columns.

The reboilers and condensers described herein may be any of a variety of process equipment suitable for changing the temperature and/or separating any of the streams described herein. In embodiments, the reboilers and the condensers may be any vessel that separates an inlet stream into a substantially vapor stream and a substantially liquid stream. These vessels typically have some internal baffles, temperature, and/or pressure control elements, but generally lack any trays or other type of complex internal structure found in other vessels. In specific embodiments, heat exchangers and kettle-type reboilers may be used as the reboilers and condensers described herein.

The heat exchangers described herein may be any of a variety of process equipment suitable for heating or cooling any of the streams described herein. Generally, heat exchangers are relatively simple devices that allow heat to be exchanged between two fluids without the fluids directly contacting each other. In the case of an air cooler, one of the fluids is atmospheric air, which may be forced over tubes or coils using one or more fans. The types of heat exchangers suitable for use with the disclosed processes and systems include shell and tube, kettle-type, air cooled, hairpin, bayonet, and plate-fin heat exchangers.

The pumps described herein may be any of a variety of process equipment suitable for increasing the pressure, temperature, and/or density of any of the streams described herein. Generally, pumps are associated with liquid streams; however such a limitation should not be read into the present processes as the pumps described herein may be interchangeable based upon the specific conditions and compositions of the streams. The types of compressors and pumps suitable for the uses described herein include centrifugal, axial, positive displacement, rotary, and reciprocating pumps. Finally, the process may contain additional pumps other than those described herein.

The mixers described herein may either be a dynamic mixer or a static mixer. Dynamic mixers are mixers that employ motion or mechanical agitation to mix two or more streams. For example, a dynamic mixer may be a tank with a paddle operating either in a continuous or batch mode. In contrast, static mixers are mixers that do not employ any motion or mechanical agitation to mix two or more streams. For example, a static mixer may be a convergence of piping designed to combine two streams, such as a pipe tee. Either type of mixer may be configured with internal baffles to promote the mixing of the feed streams.

Any of the equipment described herein may utilize energy input or output via energy streams. Such energy streams may be derived from the equipment (and process operations therein) or from any number of suitable sources. For example, heat may be added to a process stream using steam, turbine exhaust, or some other hot fluid and a heat exchanger. Similarly, heat may be removed from a process stream by using a refrigerant, air, or some other cold fluid and a heat exchanger. Alternatively, heat may be exchanged between two process streams, such as in the cross-exchanger embodiment described herein. Further, electrical energy can be supplied to compressors, pumps, and other mechanical equipment to increase the pressure or other physical properties of a fluid. Similarly, turbines, generators, or other mechanical equipment can be used to extract physical energy from a stream and optionally convert the physical energy into electrical energy. Persons of ordinary skill in the art are aware of how to configure the processes described herein with the required energy streams. In addition, persons of ordinary skill in the art will appreciate that the off-spec crude oil upgrading process may contain additional equipment, process steams, and/or energy streams other than those described herein.

The advantages of the disclosure include the transformation of an off-spec crude into valuable material by replacing C³⁻ hydrocarbons with C₄ or C₄₊ hydrocarbons. According to the techniques disclosed herein, blending of NGL or butane and then separating out the lighter hydrocarbon components (e.g., methane, ethane, propane, or combinations thereof) replaces the unexpectedly problematic fraction of C₃− hydrocarbons with heavier hydrocarbons (e.g., C₄+ hydrocarbons). It was unexpectedly found that removing the lighter hydrocarbon components while adding heavier hydrocarbons provides a desired and valuable crude oil product.

Advantages of the disclosure also include the ability to control the RVP of the crude oil product.

Advantages of the disclosure also include increasing the volume of the crude oil product by replacing the C³⁻ hydrocarbons with C₄ or C₄₊ hydrocarbons. Thus, the crude oil product not only has value compared to the off-spec crude, the volume of the crude oil product can be ten times the volume of the off-spec crude, which translates into a high volume of valuable product which is converted from the off-spec crude.

Another advantage of the disclosure is that the butane or NGL stream which is blended with the off-spec crude is sold at crude oil prices and not at NGL or butane prices. For example, butane prices can be 60% the price of crude. Thus, blending the butane NGL stream with the off-spec crude allows for the butane or NGL to be sold a crude oil prices instead of their own lower market prices.

Another advantage is by blending off-spec crude oil and NGL or butane, use of the multi-stage/tray separator avoids use of a fire-tube heat exchanger and single stage flash.

EXAMPLES

The subject matter having been generally described, the following examples are given as particular embodiments of the disclosure and are included to demonstrate the practice and advantages thereof, as well as preferred aspects and features of the inventions. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the inventions, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific aspects which are disclosed and still obtain a like or similar result without departing from the scope of the inventions of the instant disclosure. It is understood that the examples are given by way of illustration and are not intended to limit the specification of the claims to follow in any manner.

Examples of conditions and compositions of various streams of the off-spec crude oil upgrading systems and processes disclosed herein are discussed below.

Example 1

Example 1 uses the process 100 in FIG. 1 to show the conditions under which a sharp cut is taken between C₃ hydrocarbons and C₄ hydrocarbons in order to produce a valuable crude oil product, when blending the off-spec crude oil in stream 1 with the NGL in stream 2 occurs outside of the separator 150.

Example 1 was performed using Aspen HYSYS Version 8.8. In the simulation for Example 1, the separator 150 was a distillation column having sieve-type trays (also referred to herein as stages). Data for various streams depicted in FIG. 1 is shown in the Tables below.

TABLE 1 Stream Temperature Pressure Mass Flow RVP at 37.8° C. (#) (° F.) (psia) (lb/hr) (psia)  1A 90.0 50.0 2.697e+005 11.83  1 90.7 240.0 2.697e+005 11.83  2 80.0 240.0 3.364e+004 27.56  3 88.7 240.0 3.034e+005 27.56  4 200.0 237.0 3.034e+005 27.56  5 200.2 200.0 3.034e+005 27.56 10 99.01 195.0 1.038e+004 207.5 14 364.7 200.0 2.930e+005 13.41 15 268.1 195.0 2.930e+005 13.41 16 120.0 190.0 2.930e+005 13.41

TABLE 2A Stream Compositions (Mass Fraction) Component 1A 1 2 3 4 5 Nitrogen 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 CO₂ 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Methane 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 Ethane 0.0006 0.0006 0.0050 0.0011 0.0011 0.0011 Propane 0.0090 0.0090 0.2352 0.0341 0.0341 0.0341 i-Butane 0.0057 0.0057 0.0966 0.0158 0.0158 0.0158 n-Butane 0.0250 0.0250 0.3483 0.0609 0.0609 0.0609 i-Pentane 0.0148 0.0148 0.0936 0.0235 0.0235 0.0235 n-Pentane 0.0260 0.0260 0.1055 0.0348 0.0348 0.0348 n-Hexane 0.0407 0.0407 0.0535 0.0421 0.0421 0.0421 n-Heptane 0.0642 0.0642 0.0624 0.0640 0.0640 0.0640 n-Octane 0.0643 0.0643 0.0000 0.0571 0.0571 0.0571 n-Nonane 0.0499 0.0499 0.0000 0.0444 0.0444 0.0444 n-Decane 0.0538 0.0538 0.0000 0.0478 0.0478 0.0478 n-C₁₁ 0.0551 0.0551 0.0000 0.0490 0.0490 0.0490 n-C₁₂ 0.0507 0.0507 0.0000 0.0451 0.0451 0.0451 n-C₁₃ 0.0490 0.0490 0.0000 0.0436 0.0436 0.0436 n-C₁₄ 0.0444 0.0444 0.0000 0.0395 0.0395 0.0395 n-C₁₅ 0.0378 0.0378 0.0000 0.0336 0.0336 0.0336 n-C₁₆ 0.0378 0.0378 0.0000 0.0336 0.0336 0.0336 n-C₁₇ 0.0331 0.0331 0.0000 0.0294 0.0294 0.0294 n-C₁₈ 0.0331 0.0331 0.0000 0.0295 0.0295 0.0295 n-C₁₉ 0.0251 0.0251 0.0000 0.0223 0.0223 0.0223 n-C₂₀ 0.0243 0.0243 0.0000 0.0216 0.0216 0.0216 n-C₂₁ 0.0240 0.0240 0.0000 0.0214 0.0214 0.0214 n-C₂₂ 0.0252 0.0252 0.0000 0.0224 0.0224 0.0224 n-C₂₃ 0.0197 0.0197 0.0000 0.0175 0.0175 0.0175 n-C₂₄ 0.0194 0.0194 0.0000 0.0173 0.0173 0.0173 n-C₂₅ 0.0119 0.0119 0.0000 0.0106 0.0106 0.0106 n-C₂₆ 0.0161 0.0161 0.0000 0.0143 0.0143 0.0143 n-C₂₇ 0.0154 0.0154 0.0000 0.0137 0.0137 0.0137 n-C₂₈ 0.0147 0.0147 0.0000 0.0130 0.0130 0.0130 n-C₂₉ 0.0138 0.0138 0.0000 0.0123 0.0123 0.0123 n-C₃₀ 0.0516 0.0516 0.0000 0.0459 0.0459 0.0459 Benzene 0.0012 0.0012 0.0000 0.0011 0.0011 0.0011 Toluene 0.0064 0.0064 0.0000 0.0057 0.0057 0.0057 E-Benzene 0.0038 0.0038 0.0000 0.0034 0.0034 0.0034 o-Xylene 0.0071 0.0071 0.0000 0.0063 0.0063 0.0063 Cyclopentane 0.0031 0.0031 0.0000 0.0028 0.0028 0.0028 M- 0.0163 0.0163 0.0000 0.0145 0.0145 0.0145 Cyclopentane Cyclohexane 0.0057 0.0057 0.0000 0.0051 0.0051 0.0051 TOTAL 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

TABLE 2B Stream Compositions (Mass Fraction) Component 10 14 15 16 Nitrogen 0.0000 0.0000 0.0000 0.0000 CO₂ 0.0000 0.0000 0.0000 0.0000 Methane 0.0011 0.0000 0.0000 0.0000 Ethane 0.0328 0.0000 0.0000 0.0000 Propane 0.9648 0.0011 0.0011 0.0011 i-Butane 0.0010 0.0163 0.0163 0.0163 n-Butane 0.0002 0.0630 0.0630 0.0630 i-Pentane 0.0000 0.0243 0.0243 0.0243 n-Pentane 0.0000 0.0360 0.0360 0.0360 n-Hexane 0.0000 0.0436 0.0436 0.0436 n-Heptane 0.0000 0.0663 0.0663 0.0663 n-Octane 0.0000 0.0592 0.0592 0.0592 n-Nonane 0.0000 0.0460 0.0460 0.0460 n-Decane 0.0000 0.0495 0.0495 0.0495 n-C₁₁ 0.0000 0.0507 0.0507 0.0507 n-C₁₂ 0.0000 0.0467 0.0467 0.0467 n-C₁₃ 0.0000 0.0451 0.0451 0.0451 n-C₁₄ 0.0000 0.0409 0.0409 0.0409 n-C₁₅ 0.0000 0.0348 0.0348 0.0348 n-C₁₆ 0.0000 0.0348 0.0348 0.0348 n-C₁₇ 0.0000 0.0305 0.0305 0.0305 n-C₁₈ 0.0000 0.0305 0.0305 0.0305 n-C₁₉ 0.0000 0.0231 0.0231 0.0231 n-C₂₀ 0.0000 0.0224 0.0224 0.0224 n-C₂₁ 0.0000 0.0221 0.0221 0.0221 n-C₂₂ 0.0000 0.0232 0.0232 0.0232 n-C₂₃ 0.0000 0.0182 0.0182 0.0182 n-C₂₄ 0.0000 0.0179 0.0179 0.0179 n-C₂₅ 0.0000 0.0110 0.0110 0.0110 n-C₂₆ 0.0000 0.0148 0.0148 0.0148 n-C₂₇ 0.0000 0.0142 0.0142 0.0142 n-C₂₈ 0.0000 0.0135 0.0135 0.0135 n-C₂₉ 0.0000 0.0127 0.0127 0.0127 n-C₃₀ 0.0000 0.0475 0.0475 0.0475 Benzene 0.0000 0.0011 0.0011 0.0011 Toluene 0.0000 0.0059 0.0059 0.0059 E-Benzene 0.0000 0.0035 0.0035 0.0035 o-Xylene 0.0000 0.0065 0.0065 0.0065 Cyclopentane 0.0000 0.0028 0.0028 0.0028 M-Cyclopentane 0.0000 0.0150 0.0150 0.0150 Cyclohexane 0.0000 0.0053 0.0053 0.0053 TOTAL 1.0000 1.0000 1.0000 1.0000

As can be seen, in Table 1, off-spec crude oil in stream 1 having a RVP of 11.83 psia was blended with NGL in stream 2 having a RVP of 27.56 psia, and a crude oil product was recovered from the separator 150 in stream 14 and having a RVP of 13.41 psia. The crude oil product had a RVP in the range of 8-25 psia. Table 2A shows the NGL in stream 2 contained C₂-C₇ hydrocarbons. Table 2B shows the sharp cut made in the separator 150 via the compositions of stream 10 and stream 14. As can be seen in Table 2B, most of the propane was separated to flow in the reject vapors recovered in stream 10, with a small amount of propane in stream 14. Conversely, most of the butanes were separated to flow in the crude oil product in stream 14, with a small amount of butanes in stream 10. C₅₊ hydrocarbons are not found in stream 10, and C²⁻ hydrocarbons and other light compounds are not found in stream 14.

Example 2

Example 2 uses the process 200 in FIG. 2 to show a sharp cut taken between C₃ hydrocarbons and C₄ hydrocarbons when feeding an off-spec crude oil in stream 1 with a NGL in stream 2 each directly to the separator 150 such that the streams blend inside the separator 150.

Example 2 was performed using Aspen HYSYS Version 10 software. In the simulation, the separator 150 was a distillation column having sixteen sieve-type trays (also referred to herein as stages). The separator 150 had a diameter of 0.8411 feet (ft). Tray spacing was 2.0 ft. The condenser of the condenser unit 160 had a diameter of 3.914 ft and a height of 5.871 ft. The reboiler 170 had a diameter of 3.914 ft and a height of 5.871 ft. The reboil ratio of the reboiler 170 was 1.665, and the reflux ratio for the condenser unit 160 was 14.69.

Data for various streams of Example 2 as depicted in FIG. 2 is shown in the Tables below:

TABLE 3 Molar Flow (Million Standard Cubic Stream Temperature Pressure Feet Per Day RVP at 37.8° C. (#) (° F.) (psia) (MMSCFD)) (psia) 1 100.0 160.0 0.1113 25.14 2 100.0 160.0 0.1241 39.38 7 164.8 158.0 0.2366 no data 9 119.0 158.0 0.2215 no data 10 119.0 158.0 0.0151 189.4 11 217.4 161.0 0.5872 no data 12 253.8 161.0 0.3669 no data 14 253.8 161.0 0.2203 24.7

TABLE 4 Stream Compositions (Mole Fraction) Component 1 2 10 14 H₂S 0.0000 0.0000 0.0000 0.0000 Nitrogen 0.0006 0.0000 0.0045 0.0000 Oxygen 0.0000 0.0000 0.0000 0.0000 CO₂ 0.0001 0.0000 0.0009 0.0000 Methane 0.0013 0.0000 0.0100 0.0000 Ethane 0.0144 0.0000 0.1062 0.0000 Propane 0.0689 0.0100 0.5908 0.0000 i-Butane 0.0227 0.0953 0.1106 0.0575 n-Butane 0.1068 0.5224 0.1651 0.3368 i-Pentane 0.0557 0.1188 0.0061 0.0946 n-Pentane 0.0830 0.1488 0.0051 0.1254 n-Hexane 0.0776 0.1047 0.0006 0.0981 n-Heptane 0.0776 0.0000 0.0000 0.0392 n-Octane 0.0776 0.0000 0.0000 0.0392 n-Nonane 0.0776 0.0000 0.0000 0.0392 n-Decane 0.3361 0.0000 0.0000 0.1699 TOTAL 1.0000 1.0000 1.0000 1.0000

As can be seen, in Table 3, off-spec crude oil in stream 1 having a RVP of 25.14 psia was blended with NGL in stream 2 having a RVP of 39-28 psia, and a crude oil product was recovered from the separator 150 in stream 14 and having a RVP of 24.7 psia. The crude oil product had a RVP in the range of 8-25 psia. Table 4 shows the NGL in stream 2 contained C₃-C₆ hydrocarbons. Table 4 also shows the sharp cut made in the separator 150 via the compositions of stream 10 and stream 14. As can be seen in Table 4, all of the propane was separated to flow in the reject vapors recovered in stream 10, with no propane in stream 14. Conversely, most of the butanes, pentanes, and hexanes were separated to flow in the crude oil product in stream 14, with a small amount of butanes, pentanes, and hexanes in stream 10. C₇₊ hydrocarbons are not found in stream 10, and C³⁻ hydrocarbons and other light compounds are not found in stream 14.

FIGS. 5-10 illustrate graphs for various operating conditions of the separator 150 in Example 2. The separator 150 in Example 2 had 16 stages, also referred to as trays. In the graphs shown in FIGS. 5-10, tray 0 is the condenser unit 160, tray 17 is the reboiler 170, and trays 1-16 are the sixteen stages, or trays, in the separator 150 of Example 2. FIG. 5 illustrates a graph of temperature versus tray position for the distillation column in Example 2; FIG. 6 illustrates a graph of pressure versus tray position for the distillation column in Example 2; FIG. 7 illustrates a graph of vapor and liquid molar flow versus tray position for the distillation column in Example 2; FIG. 8 illustrates a graph of density and molecular weight versus tray position for the distillation column in Example 2; FIG. 9 illustrates a graph of the mole fraction of methane, nitrogen, and oxygen versus tray position for the distillation column in Example 2; and FIG. 10 illustrates a graph of the K-value for nitrogen and methane versus tray position for the distillation column in Example 2.

It is contemplated that the separator 150 of Example 1 can be operated under conditions similar to those of Example 2.

ADDITIONAL DESCRIPTION

The following embodiments are within the scope of the disclosed invention:

Embodiment 1

An off-spec crude oil upgrading process comprising: a) combining a first stream comprising an off-spec crude oil with a second stream comprising natural gas liquids (NGL) or butane to yield a blend of i) the off-spec crude oil and ii) the NGL or butane; b) separating the blend into i) an overhead stream comprising C₃− hydrocarbons and light compounds and ii) a bottom stream comprising a crude oil product comprising the NGL or butane.

Embodiment 2

The process of embodiment 1, wherein steps a) and b) are performed at an oil-production site.

Embodiment 3

The process of any of embodiments 1 and 2, wherein steps a) and b) are performed upstream of a pipeline.

Embodiment 4

The process of any of embodiments 1-3, further comprising: sending the crude oil product to a pipeline.

Embodiment 5

The process of any of embodiments 1-4, wherein the blend is formed outside of and upstream of the separator.

Embodiment 6

The process of any of embodiments 1-4, wherein the blend is formed inside the separator.

Embodiments 7

The process of embodiment 6, further comprising: feeding the first stream and the second stream separately to the separator; and recovering the overhead stream and the bottom stream from the separator.

Embodiment 8

The process of any of embodiments 1-7, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) greater than about 10 psi due to the presence of C³⁻ hydrocarbons in the off-spec crude oil.

Embodiment 9

The process of any of embodiments 1-8, wherein the crude oil product has a Reid Vapor Pressure (RVP) of about 8 psia to about 25 psia, alternatively of about 8 psia to about 14 psia, due to replacing the C³⁻ hydrocarbons with the NGL or butane of the second stream in the step of separating.

Embodiment 10

The process of any of embodiments 1-9, wherein the step of separating is performed in a distillation column.

Embodiment 11

The process of any of embodiments 1-10, wherein the separator is configured to take a sharp cut such that C₃− hydrocarbons and light compounds flow in the overhead stream and compounds of C₄ hydrocarbons and heavier are recovered in the bottom stream.

Embodiment 12

The process of any of embodiments 1-11, wherein less than about 0.1 wt % butane is contained in reject vapors recovered from the overhead stream based on a total weight of the reject vapors.

Embodiment 13

The process of any of embodiments 1-12, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the crude oil product.

Embodiment 14

The process of any of embodiments 1-13, wherein less than about 0.1 wt % butane is contained in the reject vapors based on a total weight of the blend which feeds to the separator.

Embodiment 15

The process of any of embodiments 1-14, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the blend which feeds to the separator.

Embodiment 16

An off-spec crude oil upgrading process comprising: a) combining an off-spec crude oil with natural gas liquids (NGL) or butane to yield a blend comprising i) the off-spec crude oil and ii) the NGL or butane, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) of greater than about 10 psi due to the presence of C³⁻ hydrocarbons in the off-spec crude oil; and b) controlling an amount of C₄ hydrocarbons recovered from an overhead stream of a separator such that a crude oil product produced by the separator has a Reid Vapor Pressure (RVP) of about 8 psia to about 25 psia, alternatively of about 8 psia to about 14 psia, due to the presence of natural gas liquids (NGL) or butane blended with the off-spec crude oil.

Embodiment 17

The process of embodiment 16, wherein the blend is formed outside of and upstream of the separator, the process further comprising: feeding the blend to the separator.

Embodiment 18

The process of embodiment 16, wherein the blend is formed inside the separator, the process further comprising: feeding the off-spec crude oil to the separator separately from feeding the NGL or butane to the separator; and recovering the overhead stream and a bottom stream comprising the crude oil product from the separator.

Embodiment 19

The process of any of embodiments 16-18, wherein the separator is configured to take a sharp cut such that compounds of C₃ hydrocarbons and lighter flow in the overhead stream and compounds of C₄ hydrocarbons and heavier are recovered in a bottom stream of the separator.

Embodiment 20

The process of any of embodiments 16-19, wherein steps a) and b) are performed at an oil-production site.

Embodiment 21

The process of any of embodiments 16-20, wherein steps a) and b) are performed upstream of a pipeline.

Embodiment 22

The process of any of embodiments 16-21, further comprising: sending the crude oil product to a pipeline.

Embodiment 23

The process of any of embodiments 16-22, wherein less than about 0.1 wt % butane is contained in reject vapors recovered from the overhead stream based on a total weight of the reject vapors.

Embodiment 24

The process of any of embodiments 16-23, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the crude oil product.

Embodiment 25

The process of any of embodiments 16-24, wherein less than about 0.1 wt % butane is contained in the reject vapors based on a total weight of the blend which feeds to the separator.

Embodiment 26

The process of any of embodiments 16-25, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the blend which feeds to the separator.

Embodiment 27

An off-spec crude oil upgrading system which can be used to perform any of the processes of embodiments 1-26.

Embodiment 28

The system of embodiment 27, comprising: a blend comprising i) an off-spec crude oil, and ii) natural gas liquids (NGL) or butane; and a separator configured to separate the blend into i) an overhead stream comprising C₃− hydrocarbons and light compounds and ii) a bottom stream comprising a crude oil product comprising the NGL or butane.

Embodiment 29

The system of embodiment 28, wherein the separator is located at an oil-production site where the off-spec crude oil is produced.

Embodiment 30

The system of any of embodiments 28-29, wherein the separator is distillation column.

Embodiment 31

The system of any of embodiments 28-30, wherein the blend is formed outside of and upstream of the separator.

Embodiment 32

The system of any of embodiments 28-30, wherein the blend is formed inside the separator.

Embodiment 33

The system of embodiment 32, wherein the off-spec crude oil is fed to the separator separately from the NGL or butane.

Embodiment 34

The system of any of embodiments 28-33, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) greater than about 10 psi due to the presence of C³⁻ hydrocarbons in the off-spec crude oil.

Embodiment 35

The system of any of embodiments 28-34, wherein the crude oil product has a Reid Vapor Pressure (RVP) of about 8 psia to about 25 psia, alternatively of about 8 psia to about 14 psia, due to replacing the C³⁻ hydrocarbons with the NGL or butane of the second stream in the step of separating.

Embodiment 36

The system of any of embodiments 28-35, wherein the separator is configured to take a sharp cut such that C₃− hydrocarbons and light compounds flow in the overhead stream and compounds of C₄ hydrocarbons and heavier are recovered in the bottom stream.

Embodiment 37

The system of any of embodiments 28-36, wherein less than about 0.1 wt % butane is contained in reject vapors recovered from the overhead stream based on a total weight of the reject vapors.

Embodiment 38

The system of any of embodiments 28-37, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the crude oil product.

Embodiment 39

The system of any of embodiments 28-38, wherein less than about 0.1 wt % butane is contained in the reject vapors based on a total weight of the blend which feeds to the separator.

Embodiment 40

The system of any of embodiments 28-39, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the blend which feeds to the separator.

Embodiment 41

The system of any of embodiments 28-40, further comprising a mixer configured to receive the off-spec crude oil and the NGL or butane upstream of the separator, and to form the blend.

Embodiment 42

The system of any of embodiments 28-41, further comprising a first heat exchanger configured as a cross heat exchanger, wherein the first heat exchanger is configured to cool the crude oil product to form a cooled crude oil product and to heat the blend in a blended stream to form a heated blended stream.

Embodiment 43

The system of embodiment 42, further comprising a let-down valve configured to receive the heated blended stream and to let-down a pressure of the heated blended stream to form a let-down stream, wherein the let-down stream is configured to feed the blend to the separator.

Embodiment 44

The system of any of embodiments 42-43, further comprising a second heat exchanger configured to cool the cooled crude oil product to form a further cooled crude oil product, wherein the second heat exchanger is optionally coupled to a storage tank or to a pipeline.

Embodiment 45

The system of any of embodiments, 28-44, further comprising a pre-treatment unit configured to separate an impurity from a raw crude, wherein the pre-treatment unit is configured to produce a methane stream, the off-spec crude oil, and an impurity stream.

Embodiment 46

The system of embodiment 45, wherein the mixer is configured to receive the methane stream.

Embodiment 47

The system of embodiment 45, wherein the methane stream is configured to feed directly to a top of the separator.

Embodiment 48

The system of any of embodiments 27-47, further comprising a control and/or monitoring system coupled to at least one of the overhead stream and the bottom stream, wherein the control and/or monitoring system is configured to control an amount of C₄ hydrocarbons recovered from the overhead stream of the separator such that the crude oil product produced by the separator has a Reid Vapor Pressure (RVP) of about 8 psia to about 25 psia, alternatively of about 8 psia to about 14 psia, due to the presence of NGLs or butane blended with the off-spec crude oil.

While preferred embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. The embodiments described herein are exemplary only, and are not intended to be limiting. Many variations and modifications of the invention disclosed herein are possible and are within the scope of the invention. Specifically, while the process is described in terms of a continuous process, it is contemplated that the process can be implemented as a batch process. In addition, where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of the term “optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim. Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc. Moreover, the percentages described herein may be mole fraction, weight fraction, or volumetric fraction.

Accordingly, the scope of protection is not limited by the description set out above but is only limited by the claims which follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated into the specification as an embodiment of the present invention. Thus, the claims are a further description and are an addition to the preferred embodiments of the present invention. The discussion of a reference in the herein is not an admission that it is prior art to the present invention, especially any reference that may have a publication date after the priority date of this application. The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein. 

What is claimed is:
 1. An off-spec crude oil upgrading process comprising: combining a first stream comprising an off-spec crude oil that does not meet a pipeline specification with a second stream comprising natural gas liquids (NGL) or butane to yield a blend of i) the off-spec crude oil and ii) the NGL or butane; and separating the blend into i) an overhead stream comprising C₃− hydrocarbons and light compounds and ii) a bottom stream comprising a crude oil product comprising the NGL or butane.
 2. The process of claim 1, wherein combining the first stream and the second stream and separating the blend are performed at an oil-production site.
 3. The process of claim 2, wherein combining the first stream and the second stream and separating the blend are performed upstream of a pipeline.
 4. The process of claim 1, further comprising sending the crude oil product to a pipeline.
 5. The process of claim 1, wherein the blend is formed outside of and upstream of a separator.
 6. The process of claim 1, wherein the blend is formed inside a separator.
 7. The process of claim 6, further comprising: feeding the first stream and the second stream separately to the separator; and recovering the overhead stream and the bottom stream from the separator.
 8. The process of claim 1, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) greater than about 10 pounds per square inch (psi).
 9. The process of claim 1, wherein the crude oil product has a Reid Vapor Pressure (RVP) of about 8 pounds per square inch absolute (psia) to about 25 psia.
 10. The process of claim 1, wherein separating the blend is performed in a distillation column.
 11. The process of claim 10, wherein the distillation column is configured to take a sharp cut such that C₃− hydrocarbons and light compounds flow in the overhead stream and compounds of C₄ hydrocarbons and heavier are recovered in the bottom stream, wherein the sharp cut is i) less than about 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 weight percent (wt %) butane contained in reject vapors based on a total weight of the reject vapors, ii) less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.1, or 0.01 wt % propane contained in the crude oil product based on a total weight of the crude oil product, iii) less than about 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 wt % butane contained in the reject vapors based on a total weight of the blend, iv) less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 wt % propane contained in the crude oil product based on a total weight of the blend, or v) combinations thereof.
 12. The process of claim 1, wherein less than about 0.1 weight percent (wt %) butane is contained in reject vapors recovered from the overhead stream based on a total weight of the reject vapors, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the crude oil product, wherein less than about 0.1 wt % butane is contained in the reject vapors based on a total weight of the blend, wherein less than about 10 wt % propane is contained in the crude oil product based on a total weight of the blend.
 13. An off-spec crude oil upgrading process comprising: combining an off-spec crude oil with natural gas liquids (NGL) or butane to yield a blend comprising i) the off-spec crude oil and ii) the NGL or butane, wherein the off-spec crude oil has a Reid Vapor Pressure (RVP) of greater than about 10 pounds per square inch (psi); and controlling an amount of C₄ hydrocarbons recovered from an overhead stream of a separator such that a crude oil product produced by the separator has a RVP of about 8 pounds per square inch absolute (psia) to about 25 psia.
 14. The process of claim 13, wherein the blend is formed outside of and upstream of the separator, and wherein the process further comprises feeding the blend to the separator.
 15. The process of claim 13, wherein the blend is formed inside the separator, and wherein the process further comprises: feeding the off-spec crude oil to the separator separately from feeding the NGL or butane to the separator; recovering the overhead stream and a bottom stream comprising the crude oil product from the separator.
 16. The process of claim 13, wherein combining a first stream and a second stream and separating the blend are performed at an oil-production site.
 17. The process of claim 16, wherein combining the first stream and the second stream and separating the blend are performed upstream of a pipeline.
 18. An off-spec crude oil upgrading system comprising: a blend comprising i) an off-spec crude oil and ii) natural gas liquids (NGL) or butane; and a separator configured to separate the blend into i) an overhead stream comprising C₃− hydrocarbons and light compounds and ii) a bottom stream comprising a crude oil product comprising the NGL or butane.
 19. The system of claim 18, wherein the separator is located at an oil-production site where the off-spec crude oil is produced.
 20. The system of claim 18, wherein the blend is formed outside of and upstream of the separator.
 21. The system of claim 18, wherein the blend is formed inside the separator. 